It is well known that in order to provide decorating and/or functional effect pharmaceutical formulations such as solutions, ointments, creams, tapes, patches are commonly administered.
These formulations should be applied to the skin. Thus, they are readily lost or removed under various conditions, such as perspiration, washing and external pressure. Further, they need the permeation of pharmaceutical agents into skin and diffusion to the body in order to obtain therapeutic effects. However, it is difficult to deliver sufficient pharmaceutical agents that can get therapeutic effects due to the barrier properties of skin which prohibits the entrance of foreign materials. Moreover, it is also difficult to actually deliver pharmaceutical agents to a desired site of skin.
Iontophoresis and ultrasound have been used in an attempt of transdermal delivery of cosmetics in the field of cosmetology. However, as mentioned above, it is difficult to deliver sufficient cosmetics across the skin due to the barrier properties which prohibits the entrance of foreign materials.
Recently, to solve these problems, microneedles fabricated of metal or plastic coated with pharmaceutical agents or cosmetic agents on their surface have been used as an approach to actually deliver pharmaceutical agents to a desired site of skin. However, With this approach, however, a small quantity of pharmaceutical agents or cosmetic agents can be administrated, and the accident that microneedles made of metal or plastic left in the body often happened. Thus, they are not suitable to be applied to human.
In order to overcome these defects, many studies have been made to design microneedle devices having water-soluble microneedles. For example, Patent 1 discloses a functional microneedle that has cubical or cylindrical needles of 0.5 to 500 μm in length on the substrate. And the needle is made of saccharide such as maltose which can dissolve and disappear in the body. The cross-section of the needle is square or round with a side or diameter of 0.1 to 100 μm, respectively.    [Patent] Japanese Patent No. 2003-238347